#pragma once
#include <memory>
#include <typeindex>
#include <exception>
#include <iostream>

struct Any
{
    Any(void) : m_tpIndex(std::type_index(typeid(void))) {}
    Any(const Any &that) : m_ptr(that.Clone()), m_tpIndex(that.m_tpIndex) {}
    Any(Any &&that) : m_ptr(std::move(that.m_ptr)), m_tpIndex(that.m_tpIndex) {}

    //创建智能指针时，对于一般的类型，通过std::decay来移除引用和cv符，从而获取原始类型
    template <typename U, class = typename std::enable_if<!std::is_same<typename std::decay<U>::type, Any>::value, U>::type>
    Any(U &&value) : m_ptr(new Derived<typename std::decay<U>::type>(std::forward<U>(value))),
                     m_tpIndex(std::type_index(typeid(typename std::decay<U>::type))) {}

    bool IsNull() const { return !bool(m_ptr); }

    template <class U>
    bool Is() const
    {
        return m_tpIndex == std::type_index(typeid(U));
    }

    //将Any转换为实际的类型
    template <class U>
    U &AnyCast()
    {
        if (!Is<U>())
        {
            std::cout << "can not cast " << typeid(U).name() << " to " << m_tpIndex.name() << std::endl;
            throw std::logic_error{"bad cast"};
        }

        auto derived = dynamic_cast<Derived<U> *>(m_ptr.get());
        return derived->m_value;
    }

    Any &operator=(const Any &a)
    {
        if (m_ptr == a.m_ptr)
            return *this;

        m_ptr = a.Clone();
        m_tpIndex = a.m_tpIndex;
        return *this;
    }

    Any &operator=(Any &&a)
    {
        if (m_ptr == a.m_ptr)
            return *this;

        m_ptr = std::move(a.m_ptr);
        m_tpIndex = a.m_tpIndex;
        return *this;
    }

private:
    struct Base;
    typedef std::unique_ptr<Base> BasePtr;

    struct Base
    {
        virtual ~Base() {}
        virtual BasePtr Clone() const = 0;
    };

    template <typename T>
    struct Derived : Base
    {
        template <typename U>
        Derived(U &&value) : m_value(std::forward<U>(value)) {}

        BasePtr Clone() const
        {
            return BasePtr(new Derived<T>(m_value));
        }

        T m_value;
    };

    BasePtr Clone() const
    {
        if (m_ptr != nullptr)
            return m_ptr->Clone();

        return nullptr;
    }

    BasePtr m_ptr;
    std::type_index m_tpIndex;
};
